Charles r



UNITED STATES PATENT OFFICE.

CHARLES R. RUTTKAR, OF BOONEVILLE, INDIANA, ASSIGNOR, BY DIRECT AND MESNE ASSIGNMENTS, TO AARON J. BAKER, WVI-LLIAM H. ALLEN, AND FRANK E. FORREST, ALL OF SAME PLACE.

COM POSITION FOR BLACKBOARDS.

SPECIFICATION forming part of Letters Patent No. 429,063, dated May 2'7, 1890.

Application filed November 1, 1889. Serial No. 828,939. (No specimens.)

To all whom it may concern:

Be it known that 1, CHARLES R. RUTTKAR, a citizen of the United States, residing at Booneville, in the county of WVarrick and 5 State of Indiana, have invented certain new and useful Improvements in Compositions for Blackboards; and I do declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled to in the art to which it appertains to make and use the same.

My invention has relation to plastic compositions for blackboards, and the object of the invention is to produce a composition blackboard which can be secured in place on the walls of school-roon1s and the like, as will be hereinafter more fully described, and particularly pointed out in the claim.

In carrying out my invention I first make a sheet base of plaster-of-paris of a size to correspond to the blackboard and about three-eighths or one-half inch thick. Thisis allowed to set or become nearly hard on a suitable smooth level bench or table, and

while in a semi-plastic state the upper faceis leveled off and a sheet of thin drilling or cotton applied thereto, so as to cover the entire surface thereof, and sufficient pressure or rubbing is applied to insure a union between 0 the plastic face of the plaster and the cotton. I then make a composition consisting of plaster-of-paris, two-thirds, (fig) coalsoot, powdered and sifted, one-sixth, dropblack,onetwenty-fourth, (e fineyellow sand,

5 one twenty-fourth, (7, and slaked lime one twelfth, ,)with asufficient amountof coal-tar to temper the mass. I then add enough water to constitute a plastic mass of the proper consistency, and this mass is then spread over the cotton above described to the thickness of about one-eighth of an inch, and after being evenly leveled the surface is made smooth with a plasterers float, so as to present a perfectly smooth even surface to write upon. After this is thoroughly dry a sheet of cotton is secured by a suitable glue to the back of the board,and theimproved blackboard is ready for application to the wall, where it may be secured, and at the same time a finish given to it by asuitable molding.

In practice the boards may be made and finished complete at the factory in convenient sizessay three feet wide by ten feet long and packed for transportation.

Blackboards thus constructed are extremely 5 5 durable and are not subject to warping from moisture or heat or cold, and will last indefinitely, for as the surface wearsa new surface is constantlypresented.

Having thus fully described my invention, what I claim as new and useful, and desire to secure by Letters Patent of the United States,

A composition for black-boards, consisting of plaster-of-paris, sifted coalsoot, drop- 65 black, yellow sand, slaked lime, coal-tar, and water, in about the proportions above specified.

In testimony whereof I affix my signature in presence of two witnesses.

CHARLES R. RUTTKAR.

, \Vitnesses:

AARON J. BAKER, H. J. Emma 

